25: Covering A/C Ducts

Solution: Plan Around Your Air Source

Identify the A/C vents in your room and design your room around those to keep the air flowing.

24: Too Many Photos

You're either a photo person or you're not. Photo people feel very sentimental and have a hard time giving up the pictures on their walls and tables.

Solution: Gallery Wall

Display your favorite photos in a gallery wall and switch them out whenever you'd like. You can organize the rest of your photos in albums by decade or event, and keep them nicely arranged on a bookshelf.

23: Ignoring the Foyer

The foyer is a terrific opportunity to make a statement about who you are and what your house is like. A foyer doesn't have to be something grand — any statement is better than none at all.

Solution: Make a Statement

Use paint or patterned wallpaper to add color, and hang a beautiful mirror or painting. A mirror is especially great because it reflects light and creates the illusion of more space. Use the horizontal surfaces to hold mail and keys when you first walk in.

22: Undressed Cables

A cluster of tangled wires clutters your home office and can be a hazard.

Solution: Organized Cords

Keep wires hidden at all times with these easy solutions:
1. Find a cord cover that matches your wall color.
2. If the furniture isn't a valuable antique, drill a hole in the back for the cords to go through.
3. Keep unused wires in a labeled storage container in an easily accessible area.

21: Out-of-Place Themes

A home's decor needs to be authentic and provide a sense of where you are. Decorating too much in the same print is overwhelming and tacky.

Solution: Stylish Accent Pieces

Use accents to incorporate the look you enjoy without being overwhelming. If you have a house in the mountains and love the beach, display a collection of seashells or coral in or on a bookcase or end table instead of designing an entire beach-style room.

20: Outdated Accessories

Solution: Updated Hardware

Make small changes like switching the hardware on your kitchen or bath cabinets for a big impact.

19: Lopsided Furniture

Some people just don't have an eye for furniture arrangements, so it helps to look at magazines to see what somebody else has done. If you have a sofa with a heavy bottom, don't add a big coffee table.

Solution: Balance Furniture Pieces

Use something light made of glass or with legs, and add a tall, thin floor lamp to help bring your eye up and make it more dynamic. Be sure to keep your furniture arrangements balanced to the eye.

18: Keeping Something You Hate

One of the biggest decorating mistakes is keeping things you really don't want, like an existing carpet or a gift.

Solution: Get Rid Of It

When it comes to your home, if you really hate something, just get rid of it — throw it out, give it away or donate it to charity. Drop hints to friends and family about your style to avoid receiving something that doesn't fit.

17: Too Formal

While there's nothing wrong with a very formal approach to a room, you should still make people feel comfortable in it. Too much furniture that doesn't add comfort doesn't add an inviting feel to the room.

Solution: Inviting Yet Elegant

If you have the space, use it. Give your room a function, make it livable and ensure it's welcoming.

16: Uncomfortable Dining Chairs

Never have an uncomfortable piece of furniture, especially a dining chair.

Solution: A Comfortable Place to Dine

When purchasing a dining chair, sit in it and decide if you want to be there for a long time. Also, measure the height of your dining room table before you buy chairs to make sure they're not too low or too high.

Solution: Hidden Storage

14: Everything Matches

A room that looks like it's a page from a catalog is a mistake because people don't really live that way. It's designed to sell furniture and give you an idea of what you might have in your house, but you shouldn't be matching the look that closely.

Solution: Create a Lived-In Look

Make your room's design eclectic — not like a showroom you can't live in. As you look around the room, you should see different pieces and accents that capture the eye and add interest.

Solution: Choose Your Own Style

12: Furniture That Doesn't Fit

Showrooms are much larger than your living room, so when you bring furniture into your home, the scale can be completely wrong.

Solution: Buy Right-Sized Furniture

Follow these tips to avoid buying furniture that doesn't fit:
1. Draw a to scale floor plan or purchase a room design kit so you can find the best layout without moving heavy furniture.
2. Embrace "less is more", and don't try to put too much into any space.
3. Measure the room before buying furniture pieces, and you'll decrease the chances of making a mistake.

Solution: Choose Patterns Wisely

10: Floating Rugs

Floating area rugs are a big mistake people make because it makes the room look disproportional.

Solution: A Rug That Touches All Furniture

Use measuring tape to create an outline to get a feeling of where you want the rug placed before purchasing the piece. A rug should always be connected to furniture to anchor the seating. For a successful furniture arrangement, place all the front feet of the furniture on the rug.

9: Improper Lighting

In any room in the house, you want different types of lighting for various times of the day. Dimmer switches are a great secret weapon — they're cheap, easy to install and give an entire range of control of the mood and feeling of a space.

Solution: Functional Lighting

Understand what kind of lighting you want in each space, paying attention to a room's function when determining proper lighting. For example, under-cabinet lighting is a great addition to a kitchen.

8: Frames Hung Too High

If you have to bend your neck to see your art, then it's hung too high. You generally don't want to be looking up at your artwork, whether sitting or standing.

Solution: Hang Art at Eye Level

Eye level or about 60 inches is the optimal height for hanging art and mirrors. Look at the top of your door frames and if your pieces are big enough, they should just reach the top of the door frame. To hang artwork over a sofa, make sure the bottom edge is six inches above the top of the sofa.

7: Tacky Couch Covers

If you love your furniture, there are more interesting ways to protect it other than tacky thick plastic covers.

Solution: Stylish Throws

Use a nice throw blanket that doesn't overpower the couch and accents rather than hides the piece. Keep it simple and sleek.

6: Pushed Back Furniture

Pushing furniture back all the way to the walls doesn't usually provide the best design aesthetic. The look can be too boxy and uniform.

Solution: Use a Sofa Table

Get the furniture off the walls and bring it to the center of the room. Sometimes the backs of furniture can be beautiful, and a sofa with a console table behind it is a great place for a gorgeous display.

5: Ignoring Windows

Leaving windows bare doesn't make a room feel inviting and comfortable. Besides paint, window treatments are the easiest and least expensive way to change the look of a room.

Solution: Hang Curtains High Up

A good rule of thumb is to hang curtains two inches above the frame of the window. Make the most of high ceilings by hanging them all the way up to the ceiling to make the room seem bigger. For a quick and simple look, add a Roman shade to block light and add an extra element to the space.

4: Fear of Color

Many people love color but are too scared to use it, but sticking to too much neutral won't allow you to really enjoy a room.

Solution: Paint a Wall

Try a paint color in the room to make sure you like it and that it works with the space. Live with it at various times of the day as a painted wall will appear different in the morning, afternoon and at night. If you don't like it, paint over it. Color is a great punctuation and doesn't have to be overbearing.

3: Too Many Knickknacks

Knickknacks, decorations, tchotchkes, accessories, call them what you want, but we all have too many of them, and it can make even the cleanest room seem messy.

Solution: Display Only a Few Items

Rotate what you have, and if you really like something but it's been out for a while, store it for a bit. You don't have to have it all out at once and every surface should not be covered. Edit your collections so they look good as a small grouping.

2: Pillow Overload

If the pillows actually hinder being able to sit on a couch or lie comfortably on a bed, then it's obviously too much.

Solution: Create a Serene Nook

Select a few pillows that you love to decorate your room. Instead of buying so many, spend your time, energy and money decorating a special spot just for you.

1: Fake Flowers

This is a controversial topic, but fake flowers (and plants) are a mistake. They gather dust and don't bring life into your home like real flowers, which look and smell better. Fresh flowers are expensive, but there are other things you can do instead of buying them all the time.

Solution: Display a Refreshing Fruit Centerpiece

In addition to the occasional fresh flower centerpiece, you can put lemons or other fruit in a bowl for a punch of color. Or, use some dried natural material like curly willow or bamboo stalks for a fresh look.

Not sure how to make a small space multifunctional? City-dwellers Sarah Raskin and John Kerl turned their bonus room into a guest bedroom/baby nursery with some smart decorating ideas and storage solutions.